Thunderstorms are set to interrupt the summer heatwave in Britain, with forecasters warning people across the country to "be prepared" for flooding.

The Met Office issued a yellow thunderstorm warning for Friday, with swathes of England and Wales put on notice of a risk of downpours.

The warning states some places could bring "around 20mm in an hour", while other areas will remain dry.

London and southeast England, the North West, South West, Wales and the West Midlands all face heavy showers.

Met Office meteorologist Martin Bowles said those areas which could be heaviest hit include Wales and central southern England.

"You can get a lot of rain in a short time. You can get flooding issues with people driving on roads facing large puddles," he said.

"It is a be prepared warning so it is not expected to cause problems but people need to be aware of it."

The warning states: "Heavy showers, which will most likely become thundery in places, are expected to develop quite widely across parts of England and Wales later Friday morning and through the afternoon.

"Some of the showers are likely to become focused into slow-moving bands, particularly over southwest England, with some locations receiving around 20mm in an hour.

"As is the nature of showers however, many places within the warning area will miss them altogether, and have a dry day."

Despite the downpours, which could see some lightning strikes, many people across the country will still be able to enjoy a very warm 27C-28C summer day.

Anyone in a thunderstorm area and further east could see the temperature drop to around 20C.